Cargo containers for use with chassis and for piggyback stacking on railroad cars are in wide use. The containers comprise rectangular volumes elongated sufficiently to be carried fully on a chassis and to be placed on a railroad car in a single or double stacking arrangement. The chassis is one which is sufficiently strong and rigid for hauling over a highway by a tractor if desired but normally is used only for carrying containers from and to a railroad yard or terminal and a local destination. Long distance hauling of the container is by rail car. The chassis receives a set of tandem wheels which is referred to as a bogie and which is fixed or releaseably attached to the chassis rear.
At the front of the chassis is typically a bolster assembly which is a transverse beam having a pair of spaced apart pins extending from its ends and which mate with mating apertures in a container base region typically comprising a pair of steel castings or fabricated members located at the bottom front corners of a container. The container has steel fitments at the bottom rear corners thereof each of which mate with a corresponding twist lock assembly which comprises an upstanding projection which slips into an opening in each of the steel fitments. The twist lock assembly has a lever which is manually rotated to lock each bottom rear fitment in place, locking the container to the chassis.
A railroad car includes upstanding intermediate male members which mate with a female opening in intermediate container bottom castings of the lower most container. An upper container, which rests on top of the lower container on a railroad car, includes a lower bottom steel casting arrangement. Some of the bottom castings of the upper container having a hole which aligns with a hole in an upper casting of the lower container and with the male members located in the railroad car well. The rail car male members do not have a locking arrangement. An interbox connector is manually placed into the holes of the upper castings of the lower container and into the lower bottom casting openings of the upper container. The interbox connecters include a twist lock which is manually locked in place after the upper container is assembled over the lower container. The lower container is generally about 48 feet in length whereas the upper container may be 48 feet or 53 feet in length.
When it is desired to unload the prior art containers from the railroad car, an empty chassis is brought adjacent to the railroad car via a truck tractor. A crane then lifts the upper container off the railroad car via a crane lift assembly which has bayonette fittings which mate with casting apertures in the top sides of each container. The containers each have castings at the upper region thereof at front and rear portions with top facing apertures which mate with the crane lifting mechanism. The crane lifts the container from the railroad car and places it onto the chassis and the container is then locked to the front bolster and rear twist lock assemblies of the chassis.
Typical prior art chassis are rigid elongated structures comprising a relatively heavy pair of parallel steel beams connected by spaced crossed braces. These chassis typically comprise parallel steel I beams which extend from front to rear of the chassis and are about one foot in height, 1/4 inch thick and are relatively heavy, adding weight and thus cost to the use of the chassis and container assembly for use between the rail terminal and a local destination.
The upper and lower castings of the containers tend to be relatively bulky, protrude into the interior volume of the container and take away room from cargo space within the container. Cargo space is at a premium and any additional space available for such cargo is valuable. Prior art castings at the upper header regions of the containers being relatively bulky, take up considerable room otherwise unavailable for the cargo. Such castings are located intermediate the container ends. Intermediate posts are employed for carrying loads produced by the upper container in a piggyback stacked railroad car arrangement. Prior containers, originally designed for ships having numerous stacking layers are relatively robust and heavy.
Because the prior art chassis are relatively heavy due to their rigid steel beam construction and due to the fact that prior art containers are also heavy and have castings which interfere with cargo space within the container interior, these container- chassis constructions are not as cost effective as desirable. Also, the load bearing posts of the containers are subject to bending loads due to the location of the upper load bearing casting load support axes. This causes the container support posts to require additional strength, adding weight and cost to the container.